Not long after Marat Mindiyarov started working at the Internet Research Agency, the Russian troll factory indicted by the U.S. Justice Department on Friday, he began hearing about the coveted "Facebook Department." There, workers could earn more money and work alongside a younger, hipper crowd....

As much of the country was gripped Wednesday by horrific images from the mass shooting at a Florida high school, two dozen senior Trump administration officials worked frantically into the night to thwart what they considered a different national security threat. The looming danger on the minds...